Technical Abstract:
A survey was conducted in August and September 2005 to measure tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), and resistance to acephate with a glass-vial bioassay. Plant bug populations collected from wild hosts near cotton fields from twenty locations in the Delta region of Mississippi and ten locations in the hills region of Mississippi were tested. A population near Crossett, AR was used as a standard susceptible population to which collected populations were compared for relative resistance. Six populations from the Delta and four from the hills were found to have elevated resistance to acephate as indicated by three-fold or higher resistance ratios as compared to a susceptible population. Adults from a population found near Rolling Fork, MS that had 3.6-fold resistance to acephate were tested by caging them on cotton treated with commercial insecticides at labeled rates. Mortalities in treatments with acephate at 0.5 and 1.0 lbs AI/acre at 48 h after treatment were 39 and 48%, respectively. Mortalities in treatments with dicrotophos (0.5 lbs AI/acre), cyfluthrin (0.033 lbs AI/acre) and oxamyl (0.33 lbs AI/acre) were 44, 25, and 20%, respectively. These results showed that the plant bug population from Rolling Fork had resistance to three different classes of insecticides high enough to cause control failures in the field. Plant bug populations from all thirty sample locations will be tested in May and August-September of 2006 to again determine their insecticide resistance.